The Western Australia Department of Agriculture has implemented interstate quarantine measures and sowing restrictions following the interstate discovery of Wheat Streak Mosaic Virus (WSMV).

Department executive director of plant industries Rob Delane said the virus has not been detected in WA at this stage but has been found at research sites in NSW, Victoria, South Australia, ACT and Queensland.

"The Department of Agriculture has tested more than 4700 samples from breeding and research sites around the State and all tests to date have proved negative. The negative results auger well, but we cannot state categorically that the virus is not present in Western Australia," Mr Delane said.

The vector mite species is also difficult to detect and could be present in Western Australia. The Department is undertaking surveillance for the mite in areas with favourable conditions and is also continuing its testing program for the virus. At this stage, the Department plans to continue its surveillance and testing program indefinitely.

In the meantime, under the new restrictions seed and host plants will be prohibited into WA from infested sites. The restriction relates to seed generated from last growing season onwards.

WA Quarantine Inspection Service (WAQIS) measures will be reviewed on an ongoing basis as new information and testing results become available.

Mr Delane said while the virus has had some impact on research and interstate breeding programs, international information indicated that the virus would not necessarily cause serious economic loss if it became present in WA. There are however significant benefits from preventing or delaying the establishment of the virus in WA for as long as possible.

The virus is found in many of the major grain producing regions and affects wheat, barley, corn and some grasses and may also infect oats and rye.

"Information from other countries indicates the Western Australian cropping cycle and climate may limit the spread and the impact of the virus," he said.

The approach the Department will implement is based on the following:

1. Prohibit entry or sowing of seed harvested from known infested sites in 2002/03.
2. Recommend exclusion from sowing of any seed from other high-risk interstate sites (linked to infested sites; or site with other characteristics that lead to assessment as high risk).
3. Continue trials and commercial sowings with other interstate material assessed as low risk.
4. Recommend treatment of all trial sites planted with interstate seed with miticide.
5. Plan to inspect all trial sites considered to present any WSMV risk.
6. Treat, according to a protocol, any trial planted with seed from interstate sites subsequently shown to be infected The critical determinants will be whether the plants can be adequately tested, treated and monitored. Where this cannot be achieved, measures may include destruction on a plot or trial basis.

Several sites have already been identified as being linked to infested interstate sites, including the site that has been under quarantine since the disease was first reported in Canberra. The Department considers that any WSMV risk posed by these sites can be effectively managed via testing of all plants, insecticide treatment and monitoring.

A recently sown area at another site will be sprayed with herbicide as soon as all plants emerge as this is considered the only practical means of managing the WSMV risk at that site.

More information on quarantine protection is available from WAQIS on 9311 5333 and for any issues relating to field sites contact the quarantine plant pathologist on 9368 3263.